(1) Vertical and horizontal distributions of bacterial abundance, production and ectoenzyme activities (amino peptidase and beta-glucosidase), as well as amino acid concentrations were determined in the subarctic Pacific. These microbial parameters exhibited notable east-west gradient, with generally high values in the west and low values in the east. The data suggest a large-scale regime shift of ecosystem structure in the investigated region, which appeared to be related to plankton community structure and biogeochemical variations.(2) In order to examine regulation mechanisms of organic matter - bacteria systems in marine environments, decomposition rates of polymeric carbohydrate was determined by using radio tracer techniques. Results suggest that organic matter complexation plays an important role in preservation of organic matter in marine systems.(3) Organic matter-microbial dyanamics in oceanic environments was modeled by using parameters derived from a oceanic biogeochemical data base. The analysis revealed that network virtual amplification is common in oceanic ecosystems because of intensive recylcing of organic matter withing the system.